Re: QCX-SSB: SSB with your QCX transceiver


ajparent1/KB1GMX
 

The mod interferes with cw ability due to the use of the key jack for the mic.
However the radio could before that.  A different mod could prevent that.  The
bigger issue is the code I've seen does not consider doing CW at all.  So
adding the code for that and software "switching" for that needs to be added. 
CW is easy compared to doing SSB.  Keep in mind its not an add to the QCX 
program its a wholesale replacement and leaves out a lot (all the built in digital
modes and CW reader) and I doubt all that would fit.

Q6 depending on the mod it may be an issue.  Doing EER means getting the
amplitude phase correct with frequency change or you get all manner of artifacts.

The IQ quadrature still can't go below 3 or was it 3.5 mhz.  I'm puzzled by Guidos
comments on that.  If the IQ VFO is not 90 degrees then the  RX still works but
as a simple DCRX without image rejection.  There are ways around that but
none trivial or compatible with current QCX code.

Its possible to mod the QCX to get better SSB image rejection using new constants
in the all pass and modifying the 200hz audio filter as something SSB friendly.

However read the file or go to the web site and read the basic methods are there.
Also the details of the mods to do it beside changing the code completely. And it was
done to test a specific idea, simple SSB using 8bit MPU and a class E amplifier
using the EER technique (synthesize frequency and amplitude and control the
NCO and Amplifier to assemble the resulting signal).

The whole thing is interesting to me but at best its an experimental project
for SSB.   It differs from the usual SDR as well.  If more cpu is needed to do
decent SSB then STM32F4 level 32bit MPU then going to the more common
SDR approaches for SSB is the better way to go and yields a cleaner signal.

What lacking is detailed testing of the transmitted signal quality and purity.  Doing
SSB this way can easily create all manor of trash on the band if minor details are
wrong.   

Allison

Join QRPLabs@groups.io to automatically receive all group messages.